Fix current name of the Python 3 binary on Unix (#12896).

Also fix some markup and typos.

Doc/using/unix.rst

-.. highlightlang:: none
+.. highlightlang:: sh
 
 .. _using-on-unix:
 
@@ -55,8 +55,8 @@ On FreeBSD and OpenBSD
 On OpenSolaris
 --------------
 
-To install the newest Python versions on OpenSolaris, install blastwave
-(http://www.blastwave.org/howto.html) and type "pkg_get -i python" at the
+To install the newest Python versions on OpenSolaris, install `blastwave
+<http://www.blastwave.org/howto.html>`_ and type ``pkg_get -i python`` at the
 prompt.
 
 
@@ -65,22 +65,23 @@ Building Python
 
 If you want to compile CPython yourself, first thing you should do is get the
 `source <http://python.org/download/source/>`_. You can download either the
-latest release's source or just grab a fresh `checkout
-<http://www.python.org/dev/faq/#how-do-i-get-a-checkout-of-the-repository-read-only-and-read-write>`_.
+latest release's source or just grab a fresh `clone
+<http://docs.python.org/devguide/setup#getting-the-source-code>`_.  (If you want
+to contribute patches, you will need a clone.)
 
-The build process consists the usual ::
+The build process consists in the usual ::
 
    ./configure
    make
    make install
 
 invocations. Configuration options and caveats for specific Unix platforms are
-extensively documented in the :file:`README` file in the root of the Python
+extensively documented in the :source:`README` file in the root of the Python
 source tree.
 
 .. warning::
 
-   ``make install`` can overwrite or masquerade the :file:`python` binary.
+   ``make install`` can overwrite or masquerade the :file:`python3` binary.
    ``make altinstall`` is therefore recommended instead of ``make install``
    since it only installs :file:`{exec_prefix}/bin/python{version}`.
 
@@ -98,7 +99,7 @@ For example, on most Linux systems, the default for both is :file:`/usr`.
 +-----------------------------------------------+------------------------------------------+
 | File/directory                                | Meaning                                  |
 +===============================================+==========================================+
-| :file:`{exec_prefix}/bin/python`              | Recommended location of the interpreter. |
+| :file:`{exec_prefix}/bin/python3`             | Recommended location of the interpreter. |
 +-----------------------------------------------+------------------------------------------+
 | :file:`{prefix}/lib/python{version}`,         | Recommended locations of the directories |
 | :file:`{exec_prefix}/lib/python{version}`     | containing the standard modules.         |
@@ -108,10 +109,6 @@ For example, on most Linux systems, the default for both is :file:`/usr`.
 |                                               | developing Python extensions and         |
 |                                               | embedding the interpreter.               |
 +-----------------------------------------------+------------------------------------------+
-| :file:`~/.pythonrc.py`                        | User-specific initialization file loaded |
-|                                               | by the user module; not used by default  |
-|                                               | or by most applications.                 |
-+-----------------------------------------------+------------------------------------------+
 
 
 Miscellaneous
@@ -125,11 +122,11 @@ e.g. with ::
 and put an appropriate Shebang line at the top of the script.  A good choice is
 usually ::
 
-   #!/usr/bin/env python
+   #!/usr/bin/env python3
 
 which searches for the Python interpreter in the whole :envvar:`PATH`.  However,
 some Unices may not have the :program:`env` command, so you may need to hardcode
-``/usr/bin/python`` as the interpreter path.
+``/usr/bin/python3`` as the interpreter path.
 
 To use shell commands in your Python scripts, look at the :mod:`subprocess` module.